Is Lean is mean?


> Bakers Acres wrote:

> Sir:
> My son and I had a heated discussion the other day, over whether a rich or lean engine produces more horsepower. I will stick my neck out and say that I subscribe to the opinion that ( example ) a gas can with a few drops of gas explodes, where as, a full can does not. 

> An oversimplification, but I think you get my point. Oxygen creates the explosion-gas ignites the oxygen, therefore, it would naturally follow that you "only need enough" gas to ignite the given amount of oxygen present in the cylinder-right or wrong?.

> Any help, and professional opinions, would be very much appreciated.
> Thank You.

> PS Thanks for the informative website.


From WAY too many years of looking at it the right way, err, I mean my way, err, I mean the correct way..... I mean a different way.....

Fact 1:
Too lean is bad for power and and too rich is bad for power.

Because of Fact 1:
Looking at it from a power point of view - too rich is bad and so is too lean.

And assuming:
If you have the ability to make it too rich OR too lean, you might as well make it right and get the best power.


As far as the engine goes, on new, stock 4 stroke engines, they will mechanically tolerate a bit of leanness - albeit,  with a bit less power.

Better statements:
Leaner is only meaner if you were too rich to start of with....

Richer is only badder if you were too lean to start with......

The above would be the best way to end your argument!

Conclusion 1: You are both correct - depending on where your present jetting is.

If you are too rich when making that "lean is mean" concept - you are right and vice versa.

Conclusion 2: On the other hand - if the jetting was already correct for best power,
neither one of you would be correct.

Thanks for the chance to deliver a bit of educational tuning humour!



Marc Salvisberg email:
Factory Pro Tuning
Factory Pro Dynamometer

179 Paul Drive San Rafael, CA, 94903 USA
Voice: 415 883-5620
Fax: 415 492-8803
Voice: 800 869-0497 US and Canada


Maybe in next rewrite, he'll fix the ignition timing and dyno chapters...
Otherwise great book with great starting ideas.

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